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Do not cross ScarJo.

After photos of a nude, topless Scarlett Johansson stormed the web Tuesday and Wednesday, the star has threatened to sue.

TMZ reports that Johansson's attorney sent letters of warning to various websites demanding they immediately take down "stolen copyright protected private photographs."

Confirming that the R-rated photos are indeed bonafide, the 26-year-old star's attorney Marty Singer writes: "The highly personal and private photographs at issue capture our client self-posing in her own home in a state of undress and/or topless."

Singer adds: "If you fail to comply, you will be acting at your own peril. Please govern yourselves accordingly."

TMZ also reports that Johansson's team reached out to the FBI to investigate the photo hack.